This invention concerns passenger conveyors, i.e. escalators and moving sidewalks, and particularly the control of the gap width between the foot panel of the passenger conveyor and the individual tread elements on the passenger conveyor""s tread element band.
Depending on whether they are part of an escalator or a moving sidewalk, tread elements are the steps of the step band or the pallets of the pallet band. The individual tread elements move in relation to the stationary lateral skirt or the foot panel. In order to carry out a low abrasion operation, a gap between these parts is unavoidable because of the relative movement between them. However during the operation there is a risk that objects, for example handbags, parts of clothing or the rubber soles of shoes that are particularly endangered because of sliding friction coefficients, can be drawn into this gap and get caught there. The risk is especially great on escalators, since in addition to the horizontal movement of the treads there is also a vertical movement with respect to the foot panel, which clearly increases the risk of capture in the gap.
Due to constructional conditions, the gap can not be as small as desirable. The individual tread elements of the band must have a certain play between them. In turn the tread elements move with laterally attached guiding rollers on lateral rails. A running edge is provided on both sides of the rails which guides the direction of the steps. A stationary forced guidance is not possible for technical reasons. The gap is normally adjusted for a reference measurement of 1.5 to 2.5 mm. Over time the gap size increases due to the unavoidable wear during operation. Safety code requirements establish the maximum size of the gap. For example the European norm EN 115 allows a maximum gap width of 4 mm on one side and a maximum of 7 mm is allowed for the sum of the gaps on both sides of a tread element.
Another issue is that the gap size of each individual tread element is not constant along its moving path but can continuously change for example due to a lateral back and forth movement or xe2x80x9crollingxe2x80x9d. In addition the gap sizes from tread element to tread element can possibly vary as well. To maintain the respective legal specifications, a regular control of the gap sizes is required during which these gap sizes are measured. This is an expensive undertaking because of the cited potential variations.
To avoid this problem it has been proposed to install a plastic shield on the tread elements, which is spring loaded can be shifted laterally. This device uses spring action to press the plastic shield against the skirt panel and thus closes the gap. A disadvantage is that the plastic shield grinds against the skirt panel and thereby causes undesirable noises. Beyond that the grinding causes the plastic shield to wear and also wears down the metal surface of the skirt panel, for example due to dirt particles which the plastic shield presses against the metal surface. A worn metal surface in turn abrades the plastic shield even more. In addition, many skirt panels include a low friction coating to prevent entrapments, and the wear caused by contact with the plastic shield can degrade or damage this low friction surface.
It is the task of the invention to find a solution which minimizes the required expense of controlling the gaps between tread elements and the skirt panel on passenger conveyors, and does not include the disadvantages connected with the above described device.
To that end the invention provides a gap width monitoring device which is characterized in that a gap sensor measures the gap width between the skirt panel and at least one tread element. The gap sensor is preferably connected to the passenger conveyor control and sends the gap data to the latter, so that the passenger conveyor drive is automatically switched off when a maximum distance or a maximum gap width is exceeded. Different configurations can be envisioned for the gap sensor. It can be a mechanical probe for example, or a capacitive or inductive gap measuring device. An optical measuring device can also be used, preferably of the type where the reflected backscatter light from a light beam striking the tread element surface at an angle is detected and used to determine the distance. This type of gap width monitoring has the advantage that the passenger conveyor can operate until the maximum gap width is actually exceeded. Thus the inspection intervals are not determined by the need to check the gap widths on a regular basis.
The gap sensor is preferably attached to a tread element of the passenger conveyor so that it measures the gap between this tread element and the foot panel during the operation. In that case it is advantageous to provide a wireless transmission device with a stationary transmission station, and transmission station which is attached to the tread element for transmitting the gap data from the moving tread element to the stationary transmission station. The data transmission can take place for example by using friction contacts, optical methods, particularly in the infrared range, inductive or capacitive means. In conjunction with the gap sensor and the tread element transmission station, it is furthermore especially favorable to provide a storage device for storing the gap data, and to design the tread element transmission station so that it can transmit the stored data to a stationary transmission station when it passes same. Such a stationary transmission station can be located for example in one or in both passenger conveyor reversing areas. On the one hand it can be envisioned to basically detect and evaluate only the maximum values of a run. However a number of values of a run can also be detected and evaluated. It is therefore especially preferred to design the gap width monitoring device so that a position dependent evaluation of the gap width can take place along the course of the tread element""s moving path. To that end the sensor can be advantageously connected for example to an integrated monitor circuit which provides the desired data.
The gap width monitoring device is preferably characterized in that a battery is provided to supply current to the components on the tread element side, and the transmission device is designed so that when the tread element transmission station passes the stationary transmission station, it transmits electric power for storage in the battery from the stationary transmission station to the tread element transmission station. The size of the battery can be comparatively small, since current only needs to be stored for a relatively short period of time, for example a whole or half a run. The battery can be an accumulator or a capacitor for example. The current can be transmitted by a friction contact or inductively as well. The latter is particularly preferred if the data transmission is inductive. In that case two different channels can transmit simultaneously in different directions, for example data in one direction and electric power in the other.
Furthermore a gap sensor is preferably provided on each of the opposite sides of the tread element. This allows monitoring both gap widths or the sum of the gap widths. In a first approximation it can also be assumed that the sum of the gap widths does not change significantly due to wear over time. Since this value is specified, a single sensor on one side can also provide the information about the gap widths on both sides. For example with a specified total gap width of 5 mm, the passenger conveyor control must switch off its drive motor if the gap sensor indicates values of 4 mm or greater (exceeding the permissible gap width on the sensor side), or 1 mm and less (falling short of the gap width on the opposite side of the sensor).
On escalator steps it can also occur that when the steps are offset in height with respect to each other during the rise, the gap between the step and the foot panel is different on the tread surface elevation than the gap on the front of the same step in the area where the front of the step meets the elevation of the tread surface of the next lower step. Since this gap width is also significant, it is advantageous to provide a gap sensor there as well, at least on one side.
Another gap sensor is preferably provided on the tread element for measuring the gap width between two neighboring tread element, and even more preferred is providing a deformation sensor on the tread element for measuring the deformation of the tread element due to heavy loads. It is advantageous to couple the respective sensors to the monitor circuit of the gap width monitoring device for transmission to the passenger conveyor control.
At least one stationary gap sensor is preferably provided in the passenger conveyor for measuring the gap between the skirt panel and the tread elements. This allows to determine the gap in regard to each individual tread element in a certain area of the skirt panel, for example an area which experience has shown to be particularly prone to relatively large gaps. In that case it is advantageous to provide means which permit the measured gap values to be precisely assigned to individual tread elements. The individual tread elements can have codes for example which can be detected and identified by the gap sensor, particularly by an optical gap sensor, and the applicable values are assigned to the respective step until the next code is detected.